1. Field of the Invention
The field of art to which this invention pertains is stabilization of phosphorus-vanadium-oxygen complex catalysts and in particular, the stabilization of catalysts used for the production of oxygenated products including aldehydes, ketones, acids, anhydrides, and mixtures thereof from hydrocarbon feedstocks. In a specified instance, the claimed stabilization procedure can be used on a catalyst used for the production of maleic anhydride from a specified feedstock, namely, normal butane in air. Pertinent U.S. Patent and Trademark Office classifications include Class 260, subclass 346.8.
2. Description of the Prior Art
Relevant prior art includes U.S. Pat. No. 2,773,921, issued December 11, 1956, having inventors Paul N. Rylander, Jr., and Wilford J. Zimmerschied. This patent was officially classified in Class 260-683.15, and generally relates to a phosphoric acid-vanadium-pentoxide catalyst and a hydrocarbon conversion process using the catalyst.
U.S. Pat. No. 3,915,892, issued Oct. 28, 1975, also may be considered as relevant prior art. This patent teaches a method of production of a mixed vanadium-phosphorus oxide catalyst which includes a specified procedure for dehydrating the catalyst and activating it for use in an oxidation process.
Great Britain Pat. Specification No. 1,291,354, published Oct. 4, 1972, relates to a method for the production of maleic anhydride using a phosphorus-vanadium-oxygen complex catalyst. A volatile inorganic phosphorus compound is added to a feed mixture of C.sub.4 hydrocarbons which is passed over the catalyst.
Of general interest, especially for its teaching of the specific catalyst which can be used herein, is U.S. Pat. No. 3,862,146, issued Jan. 21, 1975, having Edward M. Boghosian as its inventor. This patent teaches the oxidation of butane to maleic anhydride in the presence of phosphorus-vanadium-oxygen complex catalysts containing activators from the group of zinc, bismuth, copper, or lithium or mixtures thereof.
The presently claimed method for stabilization of phosphorusvanadium-oxygen complex catalyst is especially valuable in that a produced catalyst can quickly be broken in for use in a commercial reactor by practice of the claimed sequence of deactivation followed by reactivation. Specifically the catalyst can be contacted with a deactivating atmosphere (generally a hydrocarbon in air and preferably at a relatively high temperature) to deactivate the catalyst. Thereafter the catalyst can be contacted at reactivating conditions with an effective amount of a reactivating agent selected from a specified class of materials, the above steps are then repeated at least once. By alternately deactivating and reactivating the catalyst it eventually reaches a condition where it becomes less susceptible to deactivation.
The presently claimed stabilization method can be utilized as the final step of a catalyst preparation procedure providing a prestabilized catalyst which is ready for process use.
This stabilization procedure works for an obvious advantage in the commercial environment, since the commercial reactor will not have to be used to stabilize the catalyst.